I changed the cooler lines on my '72 Supreme this past Monday and needed to top off my fluid when I was finished. I checked it in park with engine idling and warmed up, and it looked like it was right where it needed to be.

Drove it to work this morning and all was good until I got about 3 miles away and then I noticed smoke coming from the rear of the car. Once I got to work, I checked for any obvious leaks and didn't see any other than some seepage. Checked the level and now it's about 1/2" above full, so I'm guessing I'm slightly overfilled. The fluid looked clean with no aeration or bubbles, and driveability is fine with no slippage Do I need to drain some out, or because it's such a small amount over, am I good to just let it "burn off?
For reference it's a TH400

 

You likely overfilled the transmission, it's bubbling up out of the filler tube and spilling onto the exhaust manifold or some other hot surface and making smoke. It's very difficult (in my experience) to drain out just a little bit of transmission fluid. My advice is to do what you said. Just live with it until the excess has burned off.

 

You probably had some run down the outside of the filler tube and it's burning off of a hot surface.. I would not worry about it being a little over filled.

 

Watch for drips where you park. The pan gasket, dip stick oring or your new lines could be leakng possibly because of overfill.

always check the fluid when it warm n idling

 

I did notice it dripping,, but it was residual from what I could tell.

 

Dave - "If" you did by chance overfill a little no worries - it will continue to seep out the vent until it finds its own equilibrium. As others have stated, you most likely have transmission fluid burning off the engine &/or exhaust system from spillage while filling. No worries.

 

Sounds like the general consensus is to just let it be and deal with the smoke until it settles out...I'll keep an eye on the level in the mealtime.